CN107407202A - Energy storage and conversion in free-piston combustion engines - Google Patents

Abstract

Various embodiments of the present disclosure relate to free-piston combustion engines. As described herein, the driver section may be provided in a free-piston combustion engine for storing energy during the expansion stroke. The drive section may be configured to store sufficient energy to perform a subsequent stroke. In some embodiments, the drive section may be configured to store sufficient energy to enable the engine to operate continuously throughout multiple engine cycles without electrical energy input. A linear electromagnetic machine may be provided in a free piston combustion engine for converting kinetic energy of a piston assembly into electrical energy.

Description

Energy storage and conversion in free-piston combustion engines

technical field

The present disclosure relates to a free-piston combustion engine, and more particularly, the present disclosure relates to energy storage and conversion in a free-piston combustion engine.

Contents of the invention

In some embodiments, a free piston combustion engine system is provided, comprising: a cylinder including a combustion section; at least one free piston assembly in contact with the combustion section; at least one drive section, the said at least one drive section is in contact with said at least one free piston assembly; at least one linear electromagnetic machine for direct conversion between kinetic energy and electrical energy of said at least one free piston assembly; A net electrical energy input on a subsequent stroke of the cycle, the processing circuitry causes the at least one drive segment to store at least a sufficient amount of energy from the at least one free piston assembly during an expansion stroke to perform a subsequent stroke of the piston cycle.

In some embodiments, there is provided a free piston combustion engine system comprising: a cylinder including a combustion section; at least one free piston assembly in contact with the combustion section; at least one drive section in contact with the at least a free piston assembly contact, wherein the at least one drive section is configured to store energy from the at least one free piston assembly during an expansion stroke of the piston cycle; at least one linear electromagnetic machine for driving the at least one free piston assembly direct conversion between kinetic energy and electrical energy; and processing circuitry required to cause the at least one drive segment to store at least a sufficient amount of energy from the at least one free piston assembly during the expansion stroke for the piston cycle Subsequent strokes of the piston cycle are performed without net electrical energy input during the subsequent strokes.

In some embodiments, there is provided a system for controlling a free-piston combustion engine comprising: at least one free-piston assembly in contact with a corresponding at least one drive section; and at least one linear electromagnetic machine, for directly converting kinetic energy of said at least one free piston assembly into electrical energy, said system comprising: at least one sensor coupled to a free piston combustion engine for measuring a corresponding at least one operating characteristic of the engine and for outputting a respective at least one sensor signal; at least one control mechanism for adjusting a respective at least one operating characteristic of the free-piston combustion engine based on the respective at least one control signal; and a processing circuit which takes as input the at least one sensor signal and outputting said at least one control signal, said processing circuit being configured to: process said at least one sensor signal so as to use a control mechanism to cause said at least one drive section to store a sufficient amount of gas from said at least one free piston assembly during an expansion stroke Energy to perform subsequent strokes of the piston cycle without a net input of electrical energy during the subsequent strokes of the piston cycle.

In some embodiments, a method of controlling a free-piston combustion engine is provided, the free-piston combustion engine comprising: at least one free-piston assembly in contact with a corresponding at least one drive section; and at least one linear electromagnetic machine with For converting kinetic energy of the at least one free piston assembly directly into electrical energy, the method includes: receiving at least one operating characteristic of a free piston combustion engine; processing the at least one operating characteristic using a processing circuit so as to cause the drive segment to operate at storing at least a sufficient amount of energy from the at least one free piston assembly during the expansion stroke of the piston cycle to perform a subsequent stroke of the piston cycle; and using the processing circuitry to cause the subsequent stroke of the piston cycle to be performed without net electrical energy input to the engine .

Other features and aspects will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which show, by way of example, features according to various embodiments. This summary is not intended to limit the scope of the invention, which is defined only by the appended claims.

Description of drawings

The present disclosure according to one or more different embodiments is described in detail with reference to the following figures. The drawings are provided for illustrative purposes only, and only depict typical or exemplary embodiments. These figures are provided to facilitate understanding of the concepts disclosed herein and should not be considered as limiting the breadth, scope, or applicability of these concepts. It should be noted that for clarity and ease of illustration, the drawings are not necessarily drawn to scale.

Figure 1 is a diagram of an illustrative free-piston combustion engine configuration;

2 is a cross-sectional view illustrating a dual-piston, single-combustion stage, integrated gas spring, and separate linear electromagnetic motor motor according to some embodiments of the present disclosure;

3 is a diagram illustrating a two-stroke piston cycle of the dual-piston, integrated gas spring engine of FIG. 2, according to some embodiments of the present disclosure;

4 is a cross-sectional view illustrating an alternative dual piston, separate gas spring, and separate linear electromagnetic motor motor according to some embodiments of the present disclosure;

5 is a cross-sectional view illustrating a single-piston, integrated internal gas spring motor according to some embodiments of the present disclosure;

6 is a cross-sectional view illustrating an embodiment of a gas spring rod according to some embodiments of the present disclosure;

7 is a cross-sectional view illustrating a dual-piston, integrated internal gas spring motor according to some embodiments of the present disclosure;

8 is a cross-sectional view illustrating a gas spring having an air inlet with a passive air inlet valve, according to some embodiments of the present disclosure;

9 is a cross-sectional view illustrating a gas spring with an air inlet having an active air inlet, according to some embodiments of the present disclosure;

10 is a cross-sectional view illustrating a gas spring with an air inlet according to some embodiments of the present disclosure;

11 is a cross-sectional view illustrating a gas spring with an adjustable head according to some embodiments of the present disclosure;

12 is a cross-sectional view illustrating a gas spring with adjustable components according to some embodiments of the present disclosure;

Figure 13 is a graph showing position, force and power curves during the compression and expansion strokes of a free piston engine according to some embodiments of the present disclosure;

Figure 14 is a graph showing position, force and power curves during the compression and expansion strokes of a free piston engine according to some embodiments of the present disclosure;

15 is a block diagram of an illustrative piston engine system according to some embodiments of the present disclosure;

16 shows a flowchart of illustrative steps for controlling a free piston engine, according to some embodiments of the present disclosure.

These drawings are not intended to be exclusive or to limit the disclosure to the precise form disclosed. It should be understood that the disclosed concepts and embodiments can be practiced with modification and alternatives, and that the present disclosure is limited only by the claims and the equivalents thereof.

detailed description

Various embodiments of the present disclosure relate to a free-piston, linear combustion engine characterized by high thermal efficiency. In at least one embodiment, an engine includes: (i) a cylinder including a combustion section; (ii) at least one free piston assembly in contact with the combustion section; (iii) at least one drive section that drives segment in contact with the at least one free piston assembly, the at least one drive segment storing energy during the engine expansion stroke; and (iv) at least one linear electromagnetic machine (LEM), the at least one linear electromagnetic machine in the at least one Direct conversion between kinetic and electrical energy of the free piston assembly. It should be noted, however, that additional embodiments may include various combinations of the above-described features and physical characteristics.

In general, free piston combustion engine configurations can be divided into three categories: 1) two opposing pistons, single combustion chamber; 2) single piston, two combustion chambers; and 3) single piston, single combustion chamber. A simplified diagram of three common free-piston combustion engine configurations is shown in FIG. 1 . Several illustrative examples of linear free-piston combustion engines are shown in U.S. Patent No. 8,662,029, entitled "High-efficiency linear combustion engine," filed March 4, 2014, the entire contents of which are hereby incorporated by reference incorporated into this disclosure. It should be understood that although this disclosure is presented in the context of certain illustrative embodiments of a linear free-piston combustion engine, the concepts disclosed herein can be applied to any other suitable free-piston combustion engine, including, for example, non- Linear free piston engine. A free-piston engine typically includes one or more free-piston assemblies without a mechanical linkage (e.g., a slider-crank mechanism) to convert the linear motion of the piston assembly into rotary motion or without direct control of the pistons. Kinetic mechanical linkages (eg, locking mechanisms). Free-piston engines have several advantages over such mechanically linked piston engines, which lead to increased efficiency. For example, due to the inherent architectural limitations of mechanically linked piston engines, free piston engines can be constructed with higher compression and expansion ratios, which results in higher engine efficiency, as described in previously referenced and incorporated U.S. Patent No. 8,662,029 like that. Also, free-piston engines allow for increased variability in the compression and expansion ratios, including allowing the compression ratio to be greater than the expansion ratio and allowing the expansion ratio to be greater than the compression ratio, which can also increase engine efficiency. The free-piston engine architecture also allows for enhanced control of the compression ratio based on the different cycles of the engine, which allows adjustment due to variable fuel quantities and fuel types. Additionally, due to the absence of mechanical linkages, free-piston engines result in significantly lower side loads acting on the piston assembly, which allows oil-free operation and, in turn, reduces friction and losses resulting therefrom.

FIG. 2 is a cross-sectional view illustrating one embodiment of a dual piston, single combustion stage, integrated gas spring, and split LEM free piston internal combustion engine 100 . The free-piston internal combustion engine 100 directly converts chemical energy in fuel into electrical energy via the LEM 200 . As used herein, the term "fuel" refers to a substance that reacts with an oxidizing agent. Such fuels include, but are not limited to: (i) hydrocarbon fuels such as natural gas, biogas, gasoline, diesel and biodiesel; (ii) ethanol fuels such as ethanol, methanol and butanol; (iii) hydrogen; and (iv) Any combination of the above. The engines described herein are suitable for both stationary and mobile power generation (eg, for vehicles).

The engine 100 includes a cylinder 105 having two opposing piston assemblies 120 sized to move within the cylinder 105 and meet at a combustion section 130 in the center of the cylinder 105 . Each piston assembly 120 may include a piston 125 and a piston rod 145 . The piston assembly 120 is free to move linearly within the cylinder 105 .

Referring also to FIG. 2 , the volume between the backside of the piston 125 , the piston rod 145 and the cylinder 105 is referred to herein as the drive section 160 . As used herein, "drive section" refers to the section of an engine cylinder that is capable of storing energy and providing energy to displace a piston assembly without the use of combustion. Drive segment 160 may contain a non-flammable fluid (ie, gas, liquid, or both gas and liquid) in some embodiments. In the illustrated embodiment, the fluid in drive section 160 is gas that acts as a gas spring. The drive section 160 stores energy from the expansion stroke of the piston cycle and provides energy to the subsequent stroke of the piston cycle, ie, the stroke that occurs after the expansion stroke. For example, the kinetic energy of the piston can be converted into the potential energy of the gas in the drive section during the expansion stroke of the engine. As used herein, the term "piston cycle" refers to any series of piston movements that begin and end with the piston 125 in substantially the same configuration. A common example is the four-stroke piston cycle, which includes an intake stroke, compression stroke, power stroke, and exhaust stroke. Additional alternate strokes may form part of the piston cycle, as described throughout this disclosure. A two-stroke piston cycle is characterized by a power stroke and a compression stroke. As used herein, "expansion stroke" refers to the stroke of the piston cycle during which the piston assembly moves from a top dead center ("TDC") position to a bottom dead center ("BDC") position, where TDC refers to the is the position of the piston assembly or piston assemblies when the volume of the combustion section is the smallest, while BDC refers to the position of the piston assembly or piston assemblies when the volume of the combustion section is the largest. As noted above, because the compression and expansion ratios of a free piston engine can vary or vary from cycle to cycle, in some embodiments the TDC and BDC positions can also vary or vary from cycle to cycle. Thus, as will be described in more detail below, the expansion stroke may refer to the intake stroke, the power stroke, or both the intake and power strokes. In some embodiments, the amount of energy stored by the drive segment during the expansion stroke may be determined based on various criteria and controlled by a controller and associated processing circuitry, as will be described in more detail below. For example, in some embodiments, the amount of energy stored by the drive segment during the expansion stroke may be determined based on the energy required during the subsequent stroke, ie, the stroke that occurs after the expansion stroke. In some embodiments, the controller and associated processing circuitry may cause the drive segment to store at least a sufficient amount of energy from the free piston assembly during the expansion stroke to perform the subsequent stroke in order to avoid net electrical energy input during the subsequent stroke of the piston cycle. In some embodiments, the controller and associated processing circuitry may need to cause the drive segment to store at least a sufficient amount of energy from the free piston assembly during the expansion stroke to perform subsequent strokes without net electrical energy input during the subsequent stroke. In some embodiments, the amount of energy stored by the drive segment during the expansion stroke may be greater than the amount required for subsequent strokes. For example, in the case of a two-stroke piston cycle, the drive section may store a greater amount of energy during the power stroke than is required for the subsequent compression stroke. In some embodiments, for example, in the case of a four-stroke piston cycle, the drive section may store a greater amount of energy during the power stroke than is required for the subsequent exhaust stroke. In some embodiments, for example, in the case of a four-stroke piston cycle, the drive section may store a greater amount of energy during the intake stroke than is required for the subsequent compression stroke. In some embodiments, the amount of stored energy in excess of the amount required for subsequent strokes may be converted to electrical energy by the LEM 200, as will be described in more detail below. In some embodiments, the amount of energy stored by the drive segment during the expansion stroke may be determined to enable the engine to operate continuously across successive piston cycles without requiring electrical power input from the LEM 200 . For example, the amount of energy stored by the drive segment during the expansion stroke may be determined to enable continuous operation of the engine through multiple piston cycles without requiring external power input other than that which may be required to initially start the engine.

For simplicity and clarity, the drive segment will be described herein primarily in the context of a gas spring and may be referred to herein as a "gas segment", "gas spring" or "gas spring segment". It should be appreciated that in some configurations, drive section 160 may include one or more other mechanisms in addition to or instead of gas springs. For example, such a mechanism may include one or more mechanical springs, magnetic springs, or any suitable combination thereof. In some configurations, a high efficiency linear alternator may be included that operates as a motor that may be used instead of or in addition to a spring (pneumatic, hydraulic or mechanical) for generating compression work. Those skilled in the art will appreciate that, in some embodiments, the geometry of the drive segment may be selected to minimize losses and maximize drive segment efficiency. For example, the diameter and/or dead volume of the drive segment can be selected to minimize losses and maximize drive segment efficiency. The term "dead volume" as used herein refers to the volume of the drive section when the piston assembly is in the BDC position. In some embodiments, the diameter of the drive section may be different from the combustion section in order to provide increased efficiency, for example if the drive section is a gas or hydraulic spring. Certain embodiments of gas springs are described in more detail below with reference to FIGS. 8-12 .

Combustion ignition may be achieved via, for example, compression ignition and/or spark ignition. Fuel may be injected directly into combustion chamber 130 via fuel injectors ("direct injection") and/or mixed with air prior to and/or during intake ("premix injection"). Engine 100 may operate on lean, stoichiometric, or rich combustion using liquid fuels, gaseous fuels, or both liquid and gaseous fuels, including hydrocarbons, hydrogen, ethanol, or any other suitable fuel as described above .

The cylinder 105 may include an injection port 170, an intake port 180, an exhaust port 185, and a driving gas exchange port 190 for exchanging substances (solid, liquid, gas or plasma) with the surrounding environment. As used herein, the term "port" includes any opening or set of openings (eg, porous material) that allows the exchange of matter between the interior of the cylinder 105 and its surrounding environment. It should be understood that the ports shown in Figure 2 are merely illustrative. In some configurations, fewer or more ports may be used. The above-mentioned ports may be opened and closed via a valve, or may not be opened and closed via a valve. The term "valve" may refer to any actuated flow controller or other actuated mechanism for selectively flowing a substance through an opening. The valves may be actuated by any means including, but not limited to: mechanical, electrical, magnetic, crankshaft drive, hydraulic, or pneumatic. The number, location and type of ports and valves may depend on engine configuration, injection strategy, and piston cycle (eg, two-stroke piston cycle or four-stroke piston cycle). In some embodiments, material exchange of the ports can be achieved by movement of a piston assembly that can cover and/or uncover the ports as desired to allow material exchange.

In some embodiments, the operation of drive section 160 may be adjustable. In some embodiments, the drive gas exchange port 190 can be used to control the characteristics of the drive segment. For example, the actuation gas exchange port 190 may be used to control the amount, temperature, pressure, any other suitable characteristic, and/or any combination thereof of the gas in the actuation section. In some embodiments, adjusting any of the above characteristics, and thus the amount of mass in the cylinder, can change the effective spring constant of the gas spring. In some embodiments, the geometry of drive segment 160 may be adjusted to achieve desired operation. For example, the volume of the driving section 160 may be increased or decreased by controlling the characteristics of the driving gas exchange port 190 and the driving gas flowing therein. In some embodiments, the dead volume within the cylinder can be adjusted to change the spring constant of the gas spring. It should be appreciated that any of the above-described control and regulation of drive section 160 and the gases therein may be used to control the amount of energy stored by drive section 160 during the expansion stroke of engine 100 . It should also be appreciated that the above-described control of the properties of the gases in the drive section 160 also provides variability in the frequency of the engine 100 .

Engine 100 may include a pair of LEMs 200 to convert kinetic energy of piston assembly 120 directly into electrical energy (eg, during the compression stroke, during the expansion stroke, during the exhaust stroke, and/or during the intake stroke). Each LEM 200 is also capable of converting electrical energy directly into kinetic energy for the piston assembly 120 . In some embodiments, the LEM 200 can convert electrical energy to piston kinetic energy in order to start the engine, however, once the engine has been started and sufficient fuel chemical energy is being converted to piston kinetic energy, there is no need to convert electrical energy to the piston during operation. The electrical energy is converted to kinetic energy, and at least a portion of the kinetic energy of the piston may be stored in the drive section 160 during the expansion stroke. In some embodiments, starting of the engine may be accomplished by any other suitable technique, including, for example, using stored compressed gas. As shown, the LEM 200 includes a stator 210 and a translator 220 . In particular, translator 220 is coupled to piston rod 145 and moves linearly within stator 210, which may remain stationary. Additionally, the LEM 200 can be a permanent magnet machine, an induction machine, a switched reluctance machine, or any combination thereof. Both the stator 210 and the translator 220 may include magnets, coils, iron, or any suitable combination thereof. Because the LEM 200 converts the kinetic energy of the piston directly to electrical energy and vice versa (ie, there is no mechanical linkage), mechanical and frictional losses are minimized compared to conventional engine-generator configurations. Furthermore, because LEM 200 is configured to convert a portion of the kinetic energy of the piston assembly into electrical energy during any stroke of the piston cycle, and engine 100 includes adjustable drive section 160 configured to store energy from the expansion stroke, the stored energy is can be converted to electrical energy during this period, so the LEM 200 can be constructed to have a lower capacitance than, for example, a LEM or other device that needs to convert all of the energy within a single stroke of the piston cycle (e.g., only during the expansion stroke) . Accordingly, in some embodiments, the associated linear alternator and power electronics of LEM 200 may be reduced in size, weight, and/or capacitance. This can result in reduced component size and cost, increased efficiency, increased reliability, and increased availability, as will be appreciated by those of ordinary skill in the art. Thus, in some embodiments, the frequency of the engine and thus its power output may be increased.

Those of ordinary skill in the art will understand that each LEM 200 can operate as either a generator or a motor. For example, when the LEM 200 converts the kinetic energy of the piston assembly 120 into electrical energy, they operate as a generator. When operating as a generator, the direction of force applied to translator 220 is opposite to the direction of motion of piston assembly 120 . Instead, when the LEM 200 converts electrical energy into kinetic energy for the piston assembly 120, they operate as a motor. When operating as a motor, the force applied to the translator 220 is in the same direction as the movement of the piston assembly 120 . For ease of reference, the centerline (near injection port 170 ) in FIG. 2 and corresponding figures may be considered the origin, where the positive direction for each piston assembly is in an outward direction away from the center.

The embodiment shown in Figure 2 operates using a two-stroke piston cycle. A simplified diagram of a two-stroke piston cycle 300 of the two-piston, integrated gas spring engine 100 of FIG. 2 is shown in FIG. 3 . As shown in FIG. 3 , the engine 100 may be operated using a two-stroke piston cycle that includes a compression stroke and a power stroke, wherein the piston is at BDC before the compression stroke and at TDC before the power stroke. place. Referring to the dual piston embodiment, BDC as used herein may refer to the position where the pistons are farthest from each other. Referring to the dual piston embodiment, TDC as used herein may refer to the position where the pistons are closest to each other. When at or near BDC and if the drive section is about to be used to provide compression work, the pressure of the gas within the drive section 160 is greater than the pressure of the combustion section 130, which pushes the pistons 125 away from BDC and inward toward each other, i.e., in the negative direction. Gas in drive section 160 may be used to provide some or all of the energy required to perform the compression stroke. As noted above, in some embodiments, piston 125 may be urged away from the BDC by any other suitable mechanism, including mechanical springs, magnetic springs, or any other suitable mechanism that may be used to provide compression work. While LEM 200 may also provide some of the energy required to perform the compression stroke, in a preferred embodiment, when sufficient energy is generated during combustion, sufficient energy may be stored in drive section 160 such that LEM 200 does not require Any electrical energy is converted to kinetic energy for the piston 125 because the energy stored in the drive section 160 can be transferred to the piston to provide the necessary compression work. The LEM 200 can also extract energy during the compression stroke. For example, the LEM 200 may convert a portion of the kinetic energy of the piston assembly 120 into electrical energy if the gas in the drive section 160 (or other suitable means as described above) provides excess energy for performing the compression stroke.

The amount of energy required to perform the compression stroke may depend on the desired compression ratio, the pressure and temperature of the combustion section 130 at the beginning of the compression stroke, and the mass of the piston assembly 120 . As mentioned above, the drive section 160 can provide all the energy required for the compression stroke such that no other energy input (from the LEM 200 or any other source) is required. In some embodiments, some energy may be input during the compression stroke, but the net energy during the compression stroke is still positive. The compression stroke continues until combustion occurs, which typically occurs when the velocity of the piston 125 is at or near zero. Combustion causes an increase in temperature and pressure within combustion section 130 , which pushes piston 125 outward toward LEM 200 . During the power stroke, a portion of the kinetic energy of piston assembly 120 may be converted to electrical energy by LEM 200 and another portion of the kinetic energy acts compression work on the gas in drive section 160 (or other compression mechanism). Alternatively, the entire kinetic energy of the piston assembly may be stored in the drive section 160 . The power stroke continues until the speed of the piston 125 is zero. After the power stroke and before the subsequent compression stroke, with piston 125 at or near BDC, the engine may exhaust products of combustion and intake air, an air/fuel mixture, or an air/fuel/products of combustion mixture. This treatment may be referred to herein as "breathing" or "breathing at or near the BDC." Those of ordinary skill in the art will appreciate that aeration may be accomplished in any suitable manner, such as unidirectional flow or cross-flow scavenging, as described in previously referenced and incorporated US Patent No. 8,662,029. It should also be understood that although described as occurring after the power stroke, in some embodiments, ventilation may occur during the end of the power stroke and/or during the beginning of the compression stroke. Similarly, in some embodiments, combustion may occur during the end of the compression stroke and/or during the beginning of the power stroke.

Figure 3 shows an exemplary port configuration 300 where the intake port 180 and exhaust port 185 are located near the BDC in front of the two pistons. The opening and closing of the exhaust port 185 and the intake port 180 may be independently controlled. The locations of the exhaust port 185 and the intake port 180 may be selected such that a range of compression ratios and/or expansion ratios is feasible. The number of cycles at which the exhaust port 185 and intake port 180 are activated (opening and closing) may be adjusted during and/or between cycles to change the compression ratio and/or expansion ratio and/or at the beginning of the compression stroke The amount of combustion products remaining in combustion section 130 . The combustion gases that remain in the combustion section 130 are referred to as residual gas trap (RGT) and can be used to affect combustion timing, peak combustion temperature, and other combustion and engine performance characteristics.

Although operation of a two-stroke cycle is described above, the embodiment of FIG. 2 may also operate using a four-stroke piston cycle including an intake stroke, a compression stroke, a power (expansion) stroke, and an exhaust stroke. In some embodiments, any suitable modification may be made to operate with a four-stroke piston cycle. For example, as described in previously referenced and incorporated US Patent No. 8,662,029, the port locations may be modified to operate the engine using a four-stroke piston cycle.

In some embodiments, in a four-stroke piston cycle, as described above in a two-stroke cycle, drive section 160 may provide all of the work required for the compression stroke. In some embodiments, drive section 160 may provide sufficient work to avoid net electrical energy input during the compression stroke. The compression stroke may continue until combustion occurs, for example, when the velocity of piston 125 is at or near zero. Combustion may follow a power stroke during which kinetic energy of piston assembly 120 may be stored in drive section 160 and/or converted to electrical energy by LEM 200 as described above with respect to the two-stroke cycle. At some point at or near the power stroke BDC, the exhaust port may be opened and the exhaust stroke may occur until the velocity of the piston 125 is at or near zero, which is labeled the exhaust stroke TDC for this cycle. As noted above, energy stored in drive section 160 during the power stroke may provide the work required to perform the exhaust stroke. At some point prior to exhaust stroke TDC, the combustion section 130 closes the exhaust valve while exhaust gas is still present in the cylinder. In some embodiments, this trapped exhaust may store sufficient energy to perform a subsequent intake stroke. As with the power stroke, kinetic energy of piston assembly 120 may be stored in drive section 160 and/or converted to electrical energy by LEM 200 during the intake stroke, which occurs until the velocity of piston 125 is zero. In some embodiments, drive section 160 may store sufficient energy during an intake stroke to perform a subsequent compression stroke. In some embodiments, any suitable amount of energy stored in the drive section in excess of that required for the subsequent compression stroke or the subsequent exhaust stroke may be converted to electrical energy by the LEM 200 .

4 is a cross-sectional view showing an alternate dual piston, split gas spring, and split LEM engine in accordance with the principles of the present disclosure. It should be understood that the configuration shown is for example purposes only, and that any other suitable configuration of a dual piston, split gas spring, and split LEM engine may be used in accordance with the present disclosure. Engine 400 includes a master cylinder 105 , two opposing piston assemblies 120 , and a combustion section 130 at the center of master cylinder 105 . Engine 400 is shown with certain physical differences compared to engine 100 . In particular, engine 400 includes a pair of outer cylinders 405 containing additional pistons 125 , and LEM 200 is arranged between master cylinder 105 and outer cylinders 405 . Each outer cylinder 405 includes: a drive section 410 positioned between the piston 125 and the distal end of the outer cylinder 405; and a drive rear section 420 positioned between the piston 125 and the proximal end of the outer cylinder 405 between. The master cylinder 105 includes a pair of post-combustion stages 430 disposed between the piston 125 and the distal end of the master cylinder 105 . In some embodiments, post-drive stage 420 and post-combustion stage 430 are maintained at or near atmospheric pressure. In some embodiments, post-drive stage 420 and post-combustion stage 430 are not maintained at or near atmospheric pressure. In the illustrated construction, the master cylinder 105 has a port 440 for removing blow-by gas, an injection port 170 , an intake port 180 and an exhaust port 185 . The drive gas exchange port 190 is located in the outer cylinder 405 . Each piston assembly 120 includes two pistons 125 and a piston rod 145 . The piston assembly is free to move linearly between the master cylinder 105 and the outer cylinder 405 as shown in FIG. 4 . It should be appreciated that the embodiment of FIG. 4 may utilize two-stroke piston cycle operation using, for example, the method described above with reference to FIG. .

The configuration of FIGS. 2 and 3 is shown to include a single unit referred to as engine 100 and defined by cylinder 105 , piston assembly 120 and LEM 200 . Similarly, the configuration of FIG. 4 is shown to include a single unit referred to as engine 400 and defined by master cylinder 105 , piston assembly 120 , outer cylinder 405 and LEM 200 . However, multiple units may be placed in parallel, which may be collectively referred to as "engines". This type of modular configuration, where the engine units operate in parallel, can be used to enable the engine to be scaled up according to the needs of the end user. In addition, not all units have to be the same size, operate under the same conditions (e.g., frequency, stoichiometry, or ventilation), or operate simultaneously (e.g., one or several units may be taken out of operation while one or more other unit operations). Where the units operate in parallel, there is the possibility of integration between the engines, such as, but not limited to, gas exchange between the units and/or feedback between the respective LEMs 200 of the units.

Figures 5-7 show a further embodiment featuring an integrated internal gas spring, where the gas spring is integrated inside the piston assembly and the LEM is separate from the combustor cylinder. As shown in Figures 5-7, the integrated internal gas spring (IIGS) architecture can be of similar length to the integrated gas spring with a separate LEM architecture as shown in Figures 2-3. However, the IIGS architecture can eliminate the problems associated with gas leakage from the combustion section into the gas spring, which also occurs in fully integrated gas spring and LEM architectures.

5 is a cross-sectional view illustrating a single piston, integrated internal gas spring motor according to some embodiments of the present disclosure. Several components, such as the combustion section 130, are similar to those in the previous embodiments (eg, FIGS. 1 and 2) and are numbered accordingly. Engine 500 includes cylinder 105 within which piston assembly 520 is sized to move in response to reactions within combustion section 130 near the bottom end of cylinder 105 . Piston assembly 520 includes piston 530 , piston seal 535 and spring rod 545 . The piston assembly 520 moves linearly within the cylinder 105 . In the illustrated embodiment, piston rod 545 moves along bearing 560 and is sealed by piston rod seal 555 , which is fixed to cylinder 105 . Cylinder 105 includes exhaust/injection ports 570, 580 for intake of air, fuel, exhaust, air/fuel mixture, and/or air/exhaust/fuel mixture, exhaust of combustion products, and/or injectants. Some embodiments need not have all of the ports shown in FIG. 5 . The number and type of ports depends on the engine configuration, injection strategy and piston cycle (eg, two-stroke or four-stroke piston cycle).

In the illustrated embodiment, engine 500 also includes LEM 550 (comprising stator 210 and magnets 525) for converting kinetic energy of piston assembly 520 directly into electrical energy. It should be appreciated that LEM 550 may be configured to operate in substantially the same manner as LEM 200 described above with reference to FIGS. 2-4 .

With continued reference to FIG. 5 , piston 530 includes a solid front section (combustor side) and a hollow rear section (gas spring side). The area inside the hollow section of piston assembly 520 between the front face of piston 530 and spring rod 545 includes gas as gas spring 160 that provides at least some of the work required to perform the compression stroke. Piston 530 moves linearly within combustion section 130 and within stator 210 of LEM 550 . The movement of the pistons is guided by bearings 560, 565, which may be solid, hydraulic and/or air bearings. In the illustrated embodiment, engine 500 includes both outer bearings 560 and inner bearings 565 . In particular, the outer bearing 560 is located between the combustion section 130 and the LEM 550 and the inner bearing 565 is located on the interior of the hollow section of the piston 530 . The external bearing 560 is externally fixed and does not move with the piston 530 . An inner bearing 565 is fixed to the piston 530 and moves with the piston 530 against the spring rod 545 .

With continued reference to FIG. 5 , the spring rod 545 serves as one face for the gas spring 160 and is secured externally. The spring rod 545 has at least one seal 585 located at or near the end of the spring rod for retaining gas within the gas spring segment 160 . A magnet 525 is attached to the rear of the piston assembly 520 and moves linearly with the piston assembly 520 within the stator 210 of the LEM 550 . Piston assembly 520 may have seals to keep gas in the respective segments. The illustrated embodiment includes: (i) a front seal 535 secured to the front end of the piston 530 at or near the front end to prevent gas transfer from the combustion section 130; and (ii) a rear seal 555 which The rear seal is secured to the cylinder 105 and prevents the transfer of inhaled and/or blow-by gases to the surrounding environment.

6 is a cross-sectional view illustrating an embodiment of a gas spring rod according to some embodiments of the present disclosure. In particular, the spring rod 645 includes a central lumen 610 that allows the transfer of substances between the gas spring segment 160 to a reservoir segment 620 that communicates with the surrounding environment. Communication with the ambient environment is controlled by valve 630 . The amount of substance in gas spring 646 may be adjusted to control the pressure within gas spring 645 according to some embodiments of the present disclosure.

7 is a cross-sectional view illustrating a dual-piston, integrated internal gas spring motor according to some embodiments of the present disclosure. Most of the components of the dual piston embodiment are similar to those of the single piston embodiment of Figure 5, and like elements are numbered accordingly. Additionally, the operating characteristics of the single-piston and dual-piston embodiments are similar to those described in the previous embodiments, including all aspects of the linear alternator, ventilation, combustion strategy, and the like.

As noted above, the drive segment may be implemented as a gas spring and may include one or more other mechanisms as would be understood by one of ordinary skill in the art. Various embodiments of the drive segment will be described below with reference to FIGS. 8 to 12 . Those of ordinary skill in the art will appreciate that any of the drive stages and associated mechanisms shown in FIGS. 8-12 may be suitably implemented in the free-piston engine described in FIGS. implemented in a free piston engine.

8 is a cross-sectional view illustrating a gas spring with a passively valved inlet (referred to as a "passive inlet") according to some embodiments of the present disclosure. As shown in FIG. 8 , gas spring 810 is in contact with piston assembly 820 . It should be appreciated that in some embodiments the piston assembly 820 may be a free piston assembly in contact with the combustion section as described above with reference to FIGS. 2-4 . As described above with reference to the drive segments shown in FIGS. 2-4 , the gas spring 810 is capable of storing energy and providing energy to displace the piston assembly 820 without the use of combustion. For example, energy may be stored in the gas spring due to compression of the gas in the gas spring 810 by the piston assembly 820 during the expansion stroke, and this stored energy may be used to displace the piston assembly 820 to perform a subsequent stroke, such as a compression stroke. Or the exhaust stroke.

In some embodiments, it may be desirable to adjust the operation of gas spring 810 . For example, in some embodiments it may be desirable to adjust the pressure of the gas spring by adding gas to or removing gas from the gas spring. Accordingly, as shown in FIG. 8 , intake manifold 830 may be configured to provide supplemental gas 875 to gas spring 810 via intake port 840 . It should be appreciated that intake manifold 830 may be coupled to any suitable source of pressurized gas, such as an air compressor, and that the pressure of the gas may be controlled by any suitable technique and mechanism. In some embodiments, opening and closing of air inlet 840 may be commanded by operation of passive valve 850 . As shown, the valve 850 may be coupled to a mechanical spring 860 . In some embodiments, valve 850 may be biased to a closed position by mechanical spring 860 and may move to an open position based on a change in gas pressure in gas spring 810 or a change in gas pressure in intake manifold 830 . For example, valve 850 may move to an open position when a force applied to rear surface 852 of valve 850 is greater than a force applied to front surface 854 of valve 850 . It should be understood that the force applied to the rear surface 852 may depend on the gas pressure in the intake manifold 830, the area of the rear surface 852, the spring constant associated with the mechanical spring 860, and the force required to move the valve from the closed position to the open position. The force applied to the front surface 852 may depend on the gas pressure in the gas spring 810 and the area of the front surface 854 . Thus, in some embodiments, when the gas pressure in the gas spring decreases to a certain minimum threshold, the mechanical spring 860 may "crack" causing the valve 850 to move to an open position, thereby allowing the supplemental gas 875 to flow through. Inlet 840 until the gas pressure in gas spring 810 is sufficient to cause valve 850 to move back to the closed position. As will be understood by those of ordinary skill in the art, the areas of the front surface 854 and rear surface 852, the spring constant of the mechanical spring 860, and the distance required to move the valve from the closed position to the open position can be selected and/or designed to determine the relative The "crack pressure" that can cause the valve 850 to open as described above. It should be understood that the simplified mechanical spring shown in FIG. 8 is illustrative, and that in some embodiments, instead or in addition, any suitable spring or springs may be used, including but not limited to one or more compression Springs, tension springs, torsion springs and any combination thereof. For example, the mechanical spring may comprise one or more compression coil or helical compression springs, one or more tension coil or helical tension springs, one or more torsion coil or helical torsion springs, one or more leaf springs , any other suitable spring and any suitable combination thereof.

FIG. 9 is a cross-sectional view illustrating a gas spring having an inlet with an active valve (referred to as an "active inlet") according to some embodiments of the present disclosure. Similar to FIG. 8 described above, FIG. 9 shows gas spring 910 in contact with piston assembly 920 . As described above with reference to piston assembly 820 of FIG. 8, in some embodiments piston assembly 920 may be a free piston assembly in contact with the combustion section as described above with reference to FIGS. Energy is stored and provided to displace piston assembly 920 without the use of combustion.

The gas spring 910 may operate in a similar manner to the gas spring 810 described above with its intake manifold 930 configured to provide supplemental gas 975 to the gas spring 910 via an intake port 940 . In some embodiments, opening and closing of air inlet 940 may be commanded by operation of active valve 950 . In contrast to valve 850 shown in FIG. 8 , valve 950 may be configured to be actively actuated by force applied by any suitable actuator, including electrical actuators, mechanical actuators, or Both electrical and mechanical actuators. For example, an electrical actuator can be coupled to a controller that can generate a control signal to cause the actuator to apply force to the valve 950 to move it from the closed position to the open position or from the open position to the closed position. . In some embodiments, an optional mechanical spring 960 may be coupled to the valve 950 and bias the valve in either the open position or the closed position by default.

10 is a cross-sectional view illustrating a gas spring with an air inlet according to some embodiments of the present disclosure. Similar to FIGS. 8 and 9 described above, FIG. 10 shows the drive segment or gas spring 1010 in contact with the piston assembly 1020 . As described above with reference to piston assembly 820 of FIG. 8, in some embodiments piston assembly 1020 may be a free piston assembly in contact with the combustion section as described above with reference to FIGS. Energy and provide energy to displace the piston assembly 1020 without the use of combustion. FIG. 10 shows an air inlet 1030 that may be used to provide gas to the gas spring 1010 . It should be understood that the air inlet 1030 may be coupled to any suitable source of pressurized gas, such as a compressor, and that the pressure of the pressurized gas may be controlled by any suitable technique and mechanism. The flow of gas into the gas spring 1010 can be controlled by controlling the pressure of the gas provided at the gas inlet 1030 as understood by those of ordinary skill in the art. For example, in some embodiments, gas may flow into the gas spring 1010 via the gas inlet 1030 if the pressure of the gas provided at the gas inlet 1030 is greater than the gas pressure in the gas spring 1010 . Thus, in some embodiments, the gas pressure in gas spring 1010 may be sensed by any suitable pressure sensor and adjusted by controlling the gas pressure provided via gas inlet 1030 . As noted above, in some embodiments, the drive and combustion segments, and thus the air intake 1030, may be maintained at or near atmospheric pressure. In such an embodiment, it should be appreciated that the seal 1040 is optional, as gas would be less likely to tend to leak through any gaps between the piston assembly 1020 and the surrounding housing. However, in some embodiments, the drive section, combustion section, and air intake 1030 need not be maintained at or near atmospheric pressure. In some embodiments, seal 1040 may be used to prevent gas from drive section 1010 from being wasted from drive section 1010 through any gap between piston assembly 1020 and the surrounding housing, for example, if the gas inlet is maintained at a pressure significantly above atmospheric pressure.

11 is a cross-sectional view illustrating a gas spring with an adjustable head according to some embodiments of the present disclosure. Similar to FIG. 10 , FIG. 11 shows the drive section or gas spring 1110 in contact with the piston assembly 1120 , an air inlet 1130 that may be used to supply gas to the gas spring 1110 and an optional sealing element 1160 to prevent gas from escaping. . FIG. 11 also shows adjustable head 1140 and corresponding sealing element 1150 . In some embodiments, adjustable head 1140 may be configured to change the geometry of gas spring 1110 . For example, adjustable head 1140 may translate or otherwise extend or retract in the directions shown by the arrows to increase or decrease the dead volume of gas spring 1110 . Translation, extension, retraction, or other suitable translation of adjustable head 1140 may be controlled by a controller coupled to adjustable head 1140 . It should be understood that by controlling the dead volume, the pressure of the gas in the gas spring 1110 can also be controlled provided that the gas is retained in the gas spring 1110 through the use of the sealing element 1150 and/or the optional sealing element 1160 . Accordingly, adjustable head 1140 may allow for additional control and adjustment of gas spring 1110 according to some embodiments. It should be appreciated that the above-described control and adjustment of the gas spring may allow control of the effective spring constant of the gas spring.

12 is a cross-sectional view illustrating a gas spring with adjustable components according to some embodiments of the present disclosure. Similar to FIGS. 10 and 11 , FIG. 12 shows a gas spring 1210 in contact with a piston assembly 1220 , an air inlet 1230 that may be used to supply gas to the gas spring 1210 and an optional sealing element 1250 to prevent gas from escaping. . FIG. 12 also shows adjustable member 1240 . Although three components are shown for purposes of illustration, it should be understood that any suitable number and configuration of adjustable components 1240 may be used in accordance with embodiments of the present disclosure. In some embodiments, adjustable member 1240 may be configured to change the geometry of gas spring 1210 . For example, adjustable member 1240 may be a screw, bolt, lug, or other mechanical mechanism configured to translate or otherwise extend or retract in the direction indicated by the arrow to increase or decrease the deadweight of gas spring 1210. volume. Translation, extension, retraction, or other suitable translation of adjustable member 1240 may be controlled by a controller coupled to adjustable member 1240 . It should be understood that by controlling the dead volume, the gas pressure in the gas spring 1210 can also be controlled. Thus, according to some embodiments, adjustable member 1240 may allow for additional control and adjustment of gas spring 1210 . As noted above, it should be appreciated that the above-described control and adjustment of the gas spring may allow control of the effective spring constant of the gas spring.

Figure 13 shows a plot of position, force and power curves for a free piston engine according to some embodiments of the present disclosure. As shown, the figure shows exemplary position curves 1320, force curves 1340, and power curves 1360 over time for a free-piston engine having a two-stroke piston cycle that includes a compression stroke and work stroke. Referring to the position curve 1320 , as marked in FIG. 13 , for reference purposes, the positive direction corresponds to the direction from TDC to BDC. For example, in the free piston assemblies of FIGS. 2-4 , for each free piston assembly, the centerline will correspond to the origin and the direction away from the centerline will be the positive direction. It can be seen by position curve 1320 that the piston assembly initiates the compression cycle at BDC and travels to TDC where the power cycle begins. During the power cycle, the piston assembly travels back to BDC.

Referring to force curve 1340, force is positive when force is applied in the direction from TDC to BDC. For example, in the free piston assembly of Figures 2-4, a force applied in a direction away from the centerline would be a normal force. As seen in force curve 1340, during a compression cycle, a relatively constant positive force may be applied to the piston assembly, and during a power cycle, the force may be negative (in a direction toward the centerline). It should be understood that the applied force need not be constant, and that in some embodiments a variable force profile may be applied, eg, to produce a relatively constant power output. It should also be understood that in some embodiments and as described herein, no force may be applied when the speed of the piston assembly is low, as doing so would be ineffective.

Power output is the negative product of force and velocity of the piston assembly. With particular reference to power curve 1360, it can be seen that, in the idealized situation shown, no power input to the system is required in order to perform the compression and power strokes of the piston cycle. Instead, as mentioned above, ideally, during the power stroke, there is sufficient energy stored in at least one drive section to perform the subsequent compression stroke without inputting additional energy into the system during the compression stroke.

While in an ideal situation it may be desirable to avoid any power input during operation of the compression and power strokes as described with reference to FIG. 13 , in some embodiments it may be necessary or desirable to provide some power input. Accordingly, FIG. 14 is a graph illustrating position, force and power curves for a free piston engine according to some embodiments of the present disclosure. Similar to FIG. 13 , FIG. 14 shows exemplary position curves 1420 , force curves 1440 , and power curves 1460 over time for a free-piston engine having a two-stroke piston cycle that includes a compression stroke and a work stroke. Although position curve 1420 is generally similar to position curve 1320 shown in FIG. 13 , it should be understood that force curve 1440 and power curve 1460 may differ from those shown in FIG. 13 . Referring to force curve 1440 during the compression stroke, it can be seen at 1402 that force may be applied for a brief period of time in a direction opposite to the direction it was originally applied. This is also reflected in the power curve 1460, where a negative power is seen at 1404, showing the same brief period of power input. While this force application and power input can occur for several reasons, in some embodiments this can be done in order to control the speed of the piston assembly or otherwise ensure that the piston assembly reaches the proper TDC prior to the power stroke. For example, a force may be applied to increase the velocity of the piston assembly. Similarly, with further reference to force curve 1440 during the power stroke, it can be seen at 1406 that force may be applied for a brief time in the opposite direction to the remainder of the power stroke, which is also reflected in power curve 1460, where at 1408 A negative power can be seen here, showing the same brief period of power input. As noted above, this external force and power input can occur for several reasons, but in some embodiments, the force and power input can be applied in such a way as to control the speed of the piston assembly or otherwise ensure Arrive at the proper BDC position before the stroke. For example, a force may be applied to increase the velocity of the piston assembly as described above.

Although providing input power during the compression and power strokes described with reference to FIG. 14 is not necessarily ideal operation, it should be understood that the net power input per stroke is still greater than zero (ie, there is no net power input per stroke). This is evident from the power curve 1460, where it can be seen that the integral per stroke, represented by the area of the curve above zero minus the area of the curve below zero, is significantly greater than zero. Thus, the amount of electrical energy output by the system per stroke is greater than the electrical energy input to control the position of the piston assembly as described above. As used herein, "net electrical energy" refers to the transfer of electrical energy into or out of the LEM, for example as described above with reference to FIGS. 2-4 . In some embodiments, the LEM may include a stator coupled to power electronics (including, for example, any DC bus, LGBT, and/or any other suitable components) and/or to a grid-tied inverter. Thus, in some embodiments, while some electrical energy may be input into the LEM via power electronics coupled to the LEM and/or a grid-tied inverter, the net electrical energy output from the LEM for a given stroke will be output from the LEM to the power Electronics and/or grid-connected inverters.

As noted, the embodiment described above with reference to FIGS. 2-4 includes a dual-piston, single-combustion stage, two-stroke internal combustion engine 100 . Described below and shown in the corresponding figures are control systems generally applicable to free-piston combustion engines. Thus, as noted above, the control system can be applied to other free-piston combustion engine architectures, such as that described in previously referenced and incorporated US Patent No. 8,662,029. Various modifications and alternative constructions may be utilized and other changes may be made without departing from the scope of the present disclosure, as will be understood by those of ordinary skill in the art. For example, the control system described herein can be applied, for example, to a single piston architecture in addition to the dual piston architecture described above with reference to FIGS. 2 to 4 . Similarly, the control system described here can also be applied, for example, to a four-stroke engine in addition to the two-stroke engine described above with reference to FIG. 3 .

It should be appreciated from the above disclosure that the drive section may be configured (eg, including by means of control circuitry) to avoid any need to input electrical power or net electrical power from eg the LEM during the stroke following the expansion stroke. As opposed to avoiding only occasional use of the LEM for energy input under certain conditions, in some embodiments a free-piston engine can avoid net energy input during the stroke that occurs after the expansion stroke (e.g., the compression stroke following the power stroke). And specially constructed. In some embodiments, a free piston engine may be specifically configured such that the stroke following the expansion stroke must be caused to be performed without a net electrical energy input.

15 is a block diagram of an illustrative piston engine system 1500 with a control system 1510 for a piston engine 1540 in accordance with some embodiments of the invention. Piston engine 1540 may, for example, be any suitable free piston engine, as described above with reference to FIGS. 2-7 . Control system 1510 may be in communication with one or more sensors 1530 coupled to piston engine 1540 . Control system 1510 may be configured to communicate with auxiliary systems 1520 which may be used to regulate aspects or performance of piston engine 1540 . In some embodiments, more than one piston engine may be controlled by control system 1510 . For example, control system 1510 may be configured to communicate with sensors and auxiliary systems corresponding to any number of piston engines. In some embodiments, control system 1510 may be configured to interact with a user via user interface system 1550 .

Control system 1510 may include processing device 1512, communication interface 1514, sensor interface 1516, control interface 1518, any other suitable components or modules, or any combination thereof. Control system 1510 may be at least partially implemented in one or more integrated circuits, ASICs, FPGAs, microcontrollers, DSPs, computers, terminals, control stations, handheld devices, modules, any other suitable devices, or any combination thereof. In some embodiments, the components of the control system 1510 may be communicatively coupled via a communication bus 1511 or separate communication links, as shown in FIG. 15 . Processing device 1512 may include any suitable processing circuitry, for example, one or more processors (e.g., a central processing unit), cache memory, random access memory (RAM), read only memory (ROM), any other suitable Hardware components, or any combination thereof, the processing circuitry may be configured (eg, using software, or hardwired) to process information about piston engine 1540 received by sensor interface 1516 from sensor(s) 1530 . Sensor interface 1516 may include a power supply for supplying power to sensor(s) 1530, a signal conditioner, a signal pre-processor, any other suitable component, or any combination thereof. For example, sensor interface 1516 may include filters, amplifiers, samplers, and analog-to-digital converters to condition and pre-process signals from sensor(s) 1530 . The sensor interface 1516 can communicate with the sensor(s) 1530 via a communication link 1519, which can be a wired connection (e.g., using IEEE 802.3 Ethernet or a Universal Serial Bus interface), a wireless coupling (e.g., using IEEE 802.11 "Wi-Fi" or Bluetooth), optical coupling, inductive coupling, any other suitable coupling, or any combination thereof. Control system 1510, and more particularly, processing device 1512, may be configured to control piston engine 1540 over a relevant time scale. For example, changes in one or more temperatures may be controlled in response to one or more sensed engine operating characteristics, and control may be provided on a time scale relative to piston engine operation (e.g., a response fast enough to prevent overheating and/or or component failure to adequately provide peak control as described below to allow shutdown and/or to allow adequate load following in the event of a diagnostic event).

Sensor(s) 1530 may include any suitable type of sensor that may be configured to sense any suitable property or aspect of piston engine 1540 . In some embodiments, sensor(s) may include one or more sensors configured to sense aspects and/or performance of systems in auxiliary system 1520 . In some embodiments, sensor(s) 1530 may include temperature sensors (e.g., thermocouples, resistance temperature detectors, thermistors, or optical temperature sensors) configured to sense the temperature of components of piston engine 1540, The temperature of the fluid introduced to or recovered from the piston engine 1540, or both. In some embodiments, sensor(s) 1530 may include one or more pressure sensors (e.g., piezoelectric pressure transmitters, strain-based pressure transmitters, or gas ionization sensors) configured to sense the pressure in a section of the piston engine 1540 (eg, the combustion section or the gas-driven section), the pressure of fluid introduced to or recovered from the piston engine 1540, or both. In some embodiments, sensor(s) 1530 may include one or more force sensors (e.g., piezoelectric force transducers, strain-based force transducers) configured to sense internal forces, such as tension, compression, or shear (for example, it may represent friction or other relevant force information, pressure information, or acceleration information). In some embodiments, sensor(s) 1530 may include one or more current and/or voltage sensors (e.g., an ammeter and/or voltmeter coupled to the LEM of piston engine 1540) that The voltage sensor is configured to sense voltage, current, power output and/or input (eg, current times voltage), any other suitable electrical property of piston engine 1540 and/or auxiliary system 1520 , or any combination thereof. In some embodiments, sensor(s) sensor(s) 1530 may include one or more sensors configured to sense the position of the piston assembly and/or the position of any other component of the engine, the speed of the piston assembly and/or the speed of the engine. Velocity of any other component, acceleration of the piston assembly and/or acceleration of any other component of the engine, flow rate, oxygen or nitrogen oxide emission levels, other emission levels, any other suitable performance, or any combination thereof.

Control interface 1518 may include wired connections, wireless couplings, optical couplings, inductive couplings, any other suitable couplings, or any combination thereof, to communicate with one or more of auxiliary systems 1520 . In some embodiments, control interface 1518 may include a digital-to-analog converter to provide analog control signals to any or all of auxiliary systems 1520 .

Auxiliary systems 1520 may include cooling system 1522 , pressure control system 1524 , gas drive control system 1526 , and/or any other suitable control system 1528 . Cooling/heating system 1522 may include pumps, fluid reservoirs, pressure regulators, bypasses, radiators, fluid conduits, electrical circuits (e.g., for electric heaters), any other suitable components, or any combination thereof, to Cooling, heating, or both cooling and heating are provided to the piston engine 1540 . Pressure control system 1524 may include a pump, compressor, fluid reservoir, pressure regulator, fluid conduit, any other suitable component, or any combination thereof, to supply (and optionally receive) pressure control fluid to piston engine 1540 . Gas drive control system 1526 may include a compressor, a gas reservoir, a pressure regulator, fluid conduits, any other suitable components, or any combination thereof to supply (and optionally receive) drive gas to piston engine 1540 . In some embodiments, the gas actuated control system may include any suitable components to control any of the gas spring components described above with reference to FIGS. 5-9 . In some embodiments, other systems 1528 may include a valve system, eg, a cam operating system or a solenoid system, to supply oxidant and/or fuel to piston engine 1540 .

User interface 1515 may include wired connections, wireless couplings, optical couplings, inductive couplings, any other suitable couplings, or any combination thereof, to communicate with one or more of user interface systems 1550 . User interface system 1550 may include a display 1552, an input device 1554, a mouse 1556, an audio device 1558, a remote interface accessed via a website, mobile device, or other Internet service, any other suitable user interface device, or any combination thereof. In some embodiments, the remote interface may be remote from the engine, but located near the engine site. In other embodiments, the remote interface may be remote from both the engine and the engine site. Display 1552 may include a display screen, such as a cathode ray tube fluorescent screen, a liquid crystal display, a light emitting diode display, a plasma display, any other suitable display screen that can provide graphics, text, images, or other visual effects to a user, or any other suitable display screen. combination. In some embodiments, display 1552 may include a touch screen that may provide tactile interaction with the user by, for example, providing one or more software commands on the display screen. Display 1552 may display any suitable information about piston engine 1540 (eg, a time series of piston engine 1540 performance), control system 1510, auxiliary systems 1520, user interface system 1550, any other suitable information, or any combination thereof. Input device 1554 may include a QWERTY keyboard, a numeric keypad, any other suitable set of hardware command buttons, or any combination thereof. Mouse 1556 may include any suitable pointing device that can control a cursor or icons on a graphical user interface displayed on a display screen. Mouse 1556 may include a handheld device (eg, capable of movement in two or three dimensions), a touchpad, any other suitable pointing device, or any combination thereof. Audio device 1558 may include a microphone, speakers, headphones, any other suitable device for providing and/or receiving audio signals, or any combination thereof. For example, audio device 1558 may include a microphone, and processing device 1512 may process audio commands received by user interface 1515 resulting from user voice input into the microphone.

In some embodiments, control system 1510 may be configured to receive one or more user inputs to provide control. For example, in some embodiments, control system 1510 may override control settings based on sensor feedback and base control signals to auxiliary system 1520 on one or more user inputs to user interface system 1550 . In another example, a user may enter a setpoint value for one or more control variables (e.g., temperature, pressure, flow rate, work input/output, or other variables), upon which the control system 1510 may Execute the control algorithm.

In some embodiments, operating characteristics (eg, one or more desired performance values for piston engine 1540 or auxiliary system 1520 ) may be predefined by the manufacturer, the user, or both. For example, certain operating characteristics may be stored in memory of the processing device 1512 and may be accessed to provide one or more control signals. In some embodiments, one or more of the operational characteristics may be changed by the user. Control system 1510 may be used to maintain, adjust, or otherwise manage those operating characteristics.

As noted above, in some embodiments, the drive section may be configured to store a specific amount of energy during the engine's expansion stroke. In some embodiments, as described above, the drive segment may be configured to store sufficient energy during expansion to provide the energy required for a subsequent stroke, ie, to provide the energy required for a stroke that occurs after the expansion stroke. For example, in an engine having a two-stroke cycle, the drive section may be configured to store sufficient energy during expansion to provide the energy required for the subsequent compression stroke. In an engine having a four-stroke cycle, for example, the drive section may be configured to store sufficient energy during the expansion stroke to provide the energy required for the subsequent exhaust stroke. In some embodiments, the drive segment may be configured to store more energy than is required for subsequent strokes. In some embodiments, excess energy, or a portion of the excess energy, stored in the drive segment may be converted to electrical energy by one or more LEMs during subsequent strokes. For example, one or more LEMs may be configured to extract work during a power stroke of a free-piston combustion engine by converting a portion of the kinetic energy of the piston assembly into electrical energy. In some embodiments, the one or more LEMs may also be configured to extract at least some of the work provided by the drive section during the compression stroke of the free-piston combustion engine. That is, the potential energy stored in the drive section during the expansion stroke is converted into kinetic energy of the piston assembly during the subsequent stroke. At least some of this kinetic energy may be converted to electrical energy by one or more LEMs during subsequent strokes. It will be appreciated that, as described above, when LEMs are configured to extract electrical energy during the expansion stroke and subsequent strokes, their size and/or weight can be reduced, thereby reducing material weight and cost.

In some embodiments, the amount and manner of energy stored in the drive segment and extracted by the LEM can be controlled, eg, by control system 1510 . For example, sensor 1530 may be used to measure any one or more operating characteristics of a free-piston combustion engine, e.g., position of piston assembly, velocity of piston assembly, acceleration of piston assembly, pressure in the combustion section, temperature in the combustion section , the potential energy of the combustion section, the chemical energy in the combustion section, the pressure in the driving section (for example, the pressure of the spring used as the above-mentioned driving section or the pressure of the driving gas), the potential energy of the driving section (for example, the pressure of the driving section used as the above-mentioned spring force or potential energy of the driving gas), temperature of the gas in the driving section, electrical output, indicated work of the burner or driving section, electrical efficiency, indicated efficiency of the burner or driving section, LEM (eg, stator or magnet) Temperature, combustor air flow rate, combustor fuel flow rate, drive section make-up air flow rate, temperature of the piston assembly, previous cycle performance, ambient temperature and pressure (e.g., in the area surrounding the engine), emissions characteristics, any Other suitable properties, or any suitable combination thereof. Using sensor interface 1516 , control system 1510 may generate one or more signals representative of one or more sensed characteristics that are input into processing device 1512 .

Processing device 1512 may generate one or more control signals based at least in part on signals received from sensor 1530 and sensor interface 1516 . In some embodiments, processing device 1512 may determine the amount of energy required for a given piston stroke based on signals received from sensor 1530 and sensor interface 1516, and the control signal may be used by processing device 1512 to control energy stored as potential energy in the drive section. The amount of kinetic energy of the piston assembly in . The processing device 1512 may also determine how much kinetic energy of the piston assembly is converted to electrical energy and cause this conversion to occur using any suitable control mechanism. As used herein, the term "control mechanism" may refer to any suitable software, hardware and techniques, and any suitable combination thereof, for controlling any of the operational characteristics described above to achieve a desired result. For example, one or more control signals may control the operating characteristics of the engine so as to store in the drive section the energy required for subsequent strokes that have been determined to be required by the processing device 151 . For example, one or more control signals may control the operating characteristics of the engine so as to cause a desired amount of kinetic energy of the piston assembly to be stored in the drive section during the expansion stroke of the engine and subsequently cause the desired amount of kinetic energy of the piston assembly to be generated by LEMs are converted into electrical energy. As noted above, the energy required for subsequent strokes (e.g., compression or exhaust strokes) may depend on the desired compression ratio, the pressure and temperature of the combustion section at the beginning of the subsequent stroke, the mass of the piston assembly, the desired timing of combustion , atmospheric pressure, ambient temperature, and other desired phasing characteristics with respect to the engine. The amount of kinetic energy to be converted to electrical energy may be determined based on the difference between the amount stored in the drive section during the expansion stroke and the amount required for the subsequent stroke, which may depend at least in part on desired parameters associated with the engine. In some embodiments, it may be based on desired power output from the engine, desired emissions output from the engine, desired efficiency of the engine, desired load following, any other desired parameter, or other Any suitable combination determines the amount of kinetic energy to be converted into electrical energy. For example, if the drive section becomes inefficient, the amount of kinetic energy converted to electrical energy during the power stroke may be increased, and the amount of kinetic energy converted to electrical energy during the compression stroke may be decreased. Alternatively, the amount of kinetic energy converted to electrical energy during the power stroke may be reduced, and the amount of kinetic energy converted to electrical energy during subsequent strokes may be increased, for example, if the drive segment becomes more efficient.

In addition to controlling the amount of kinetic energy of the piston assembly that is converted to electrical energy, a control signal can be used to control the manner in which the LEM converts kinetic energy to electrical energy. For example, the control signal may cause switching to occur in either direction at a constant rate, a non-constant rate, a variable rate, or any combination thereof.

In some embodiments, the processing device 1512 may use one or more parameters of the free-piston combustion engine to determine the amount of work extracted during the compression stroke of the engine. In some embodiments, desired parameters may be input by a user via user interface system 1550 . For example, a user may input a desired power output of a free-piston combustion engine via user interface system 1550 . In other embodiments, the desired parameters may be received from an external device via the communication interface 1514 . For example, a desired power output representing a desired power output based on historical power requirements, future predicted power requirements, or any suitable combination thereof may be received from an external device.

In some embodiments, the processing device 1512 may determine one or more operating characteristics of the engine that yield the desired parameter based on any suitable relationship between the parameter and the one or more operating characteristics. For example, the processing device 1512 may determine the velocity, acceleration, or other operating characteristic of the piston(s) based on the desired power output and the relationship of the operating characteristics to the desired power output. Processing device 1512 may then determine the amount of compression work required to produce the operating characteristic determined by processing device 1512 . Based on the desired amount of compression work, the processing device 1512 may control the engine to extract an appropriate amount of work during the engine compression stroke such that the remaining compression work acting on the piston will produce the desired operating characteristic or characteristics, with the desired The desired operating characteristic or characteristics will in turn produce the desired power output. Although the above embodiments are described in terms of desired power output, as noted above, the processing device can be optimized based on the engine's desired efficiency, desired emissions output, desired load following, or any other suitable parameter The operating characteristics of the engine.

In some embodiments, the above described work extraction, engine parameters and operating characteristics may be coordinated among several piston engines controlled by the control system 1510 . For example, kinetic energy of one piston engine may be converted to electrical energy and the resulting electrical energy may be converted to electrical energy of another piston engine based on desired engine parameters, corresponding operating characteristics, and the amount of work required for compression and/or exhaust strokes. kinetic energy.

Although the above embodiments are described in terms of work extraction during the compression stroke or exhaust stroke of a free-piston combustion engine, those skilled in the art will readily appreciate that, in some embodiments, the control system 1510 can be more The conversion of kinetic energy to electrical energy and electrical energy to kinetic energy is commonly used. In some embodiments, the kinetic energy of the piston may be continuously converted to electrical energy during engine operation regardless of the engine stroke or cycle. In some embodiments, the kinetic energy of the piston assembly may be continuously converted to electrical energy during engine operation regardless of the stroke or cycle of the engine. In other embodiments, regardless of any desired or required work extraction, the control system 1510 may apply arbitrary forces to one or more piston assemblies of the engine based on any desired engine parameters or operating characteristics. For example, control system 1510 may control the operating characteristics of the engine to apply force to the two pistons in order to synchronize the two pistons so that they reach TDC and/or BDC substantially simultaneously. As another example, the control system 1510 may control the operating characteristics of the engine to apply force to the pistons in order to phase separate the engines so that they are not operating simultaneously on the same engine cycle in order to provide a more continuous flow of power. As another example, control system 1510 may control operating characteristics of the engine to obtain a desired peaking of the piston.

FIG. 16 shows a flowchart 1600 of illustrative steps for controlling a free piston engine, according to some embodiments of the present disclosure. It should be appreciated that the foregoing steps may utilize any suitable free piston engine and/or free piston engine system or components thereof described above in relation to FIGS. 2-12 or any other suitable free piston engine or free piston engine system.

Step 1602 includes receiving engine operating characteristics from sensors. In some embodiments, engine operating characteristics may be received by processing device 1512 or any processing circuitry thereof from sensor 1530 via sensor interface 1216 as described above with respect to FIG. 15 . In some embodiments, the engine operating characteristics may include any of the above operating characteristics or any suitable combination thereof. For example, the processing device 1512 may receive the compression ratio, the pressure and temperature of the combustion section, and the mass of the piston assembly. In some embodiments, processing device 1512 may receive engine operating characteristics that provide information about the kinetic energy of the piston assembly from sensor 1530 via sensor interface 1516 described above. In some embodiments, processing device 1512 may receive engine operating characteristics that provide information from sensors 1530 via sensor interface 1516 described above regarding the amount of energy that may be stored in the drive segment.

Step 1604 includes generating at least one control signal based on the operating characteristic received in step 1602 . In some embodiments, processing device 1512 or any processing circuitry thereof may generate one or more control signals based on the operating characteristics received in step 1602 . For example, the processing device 1512 may generate control signals that can be used to adjust any of the desired aspects or performances of the piston engine 1540 described above with reference to FIG. Amount of energy to perform subsequent strokes of the piston cycle. In some embodiments, processing device 1512, or any processing circuitry thereof, may generate control signals to cause the drive section of piston engine 1540 to store a sufficient amount of energy during the expansion stroke of the piston cycle in order to avoid the subsequent stroke of the piston cycle. Medium net electrical energy input. In some embodiments, processing device 1512, or any processing circuitry thereof, may generate control signals required to cause the drive section of piston engine 1540 to store a sufficient amount of energy during the expansion stroke of the piston cycle so that there is no Subsequent strokes of the piston cycle are executed with a net electrical energy input. In some embodiments, the subsequent stroke may include a compression stroke. In some embodiments, the subsequent stroke may include an exhaust stroke.

In some embodiments, the processing device may receive any of the aforementioned operating characteristics and generate the control signal in steps 1602 and 1604 in a manner that takes into account changes in the operating characteristics over time. For example, the processing device may receive the position, velocity and/or acceleration of the piston assembly over time and generate control signals to adjust the operating characteristics accordingly. In some embodiments, the processing device may receive engine operating characteristics that periodically provide information about the kinetic energy of the piston assembly from sensor 1530 via sensor interface 1516 described above and generate updated control signals accordingly. In some embodiments, the processing device may receive engine operating characteristics that periodically provide information from sensor 1530 via sensor interface 1516 described above regarding the amount of energy that may be stored in the drive section and determine updated control signals accordingly. In some embodiments, the relevant operating characteristics may be received and the control signals may be generated at any suitable frequency such that changes in the operating characteristics over time may be taken into account prior to subsequent strokes. For example, the operating characteristic may be received and analyzed at a frequency that allows the operating characteristic to be evaluated multiple times per stroke (eg, 100 Hz to 100 khz).

In some embodiments, the processing device may take into account losses that are expected to occur in the energy storage and conversion process when generating any control signals in step 1604 . For example, the processing device may determine the amount of energy required for subsequent strokes or the amount of energy stored in the drive section based on known or predictable friction losses, heat losses, or any other suitable losses related to energy storage and/or conversion . In some embodiments, the processing device may allow for unexpected loss in generating any control signals in step 1604 . For example, in determining the amount of energy required for a subsequent stroke, the processor may add a buffer amount of energy to account for unexpected losses that occur during execution of the subsequent stroke. As another example, when determining the amount of energy stored in the drive section during the expansion stroke, the processor may add a buffer amount of energy to account for unexpected losses in storing energy in the drive section during the expansion stroke.

Step 1606 includes, based on one or more of the control signals generated in step 1604, causing an amount of energy to be stored in the drive segment during the expansion stroke. In some embodiments, processing device 1512, or any processing circuitry thereof, may transmit control signals to any of auxiliary systems 1520 via control interface 1518 in order to adjust aspects or performance of piston engine 1540 such that a desired amount of of energy is stored in the drive section. For example, the control signal may be operative to regulate the pressure of the drive segment by commanding the gas drive control system 1526 to add gas to or remove gas from the drive segment via the intake port so that during the expansion stroke Store a certain amount of energy. In some embodiments, the control signal may be operative to adjust the dead volume of the cylinder by adjusting the settings of any of the auxiliary systems 1520 . In some embodiments, the control signal may be operative to adjust any suitable performance of the gas spring using any of the mechanisms described above with respect to FIGS. 8-12 . In some embodiments, as described above with reference to steps 1504 and 1506, the processing device may generate control signals and communicate with the piston engine and/or its auxiliary systems at any suitable frequency so that operating characteristics can be considered before subsequent strokes occur. changes over time. For example, a processing device may generate control signals and communicate with the piston multiple times per stroke to ensure responsiveness to changing operating characteristics.

Step 1608 includes, based on one or more of the control signals generated in step 1604, causing an amount of kinetic energy of the piston assembly to be converted to electrical energy. In some embodiments, the processing device 1512, or any processing circuitry thereof, may determine the amount of kinetic energy of the at least one free piston assembly that is converted to electrical energy, and may, based on that amount, cause the at least one LEM to convert a certain amount of the free piston assembly Kinetic energy is converted into electrical energy. In some embodiments, the processing device 1512 may cause the at least one LEM to directly convert an amount of kinetic energy of the at least one free piston assembly into electrical energy during the expansion stroke of the piston cycle. In some embodiments, the one or more processors of the processing device 1512 may cause the at least one LEM to convert the kinetic energy of the at least one free piston assembly into electrical energy during a subsequent stroke of the piston cycle. For example, processing device 1512 may cause at least one LEM to convert kinetic energy of the at least one free piston assembly to electrical energy during any of an expansion stroke, compression stroke, exhaust stroke, intake stroke, or any combination thereof. For example, the one or more processors of the processing device 1512 may cause the at least one LEM to convert the same amount of kinetic energy of the at least one free piston assembly into electrical energy during the expansion stroke and subsequent strokes of the piston cycle. In some embodiments, the amount of kinetic energy converted to electrical energy by the at least one LEM may be determined such that at least a predetermined minimum percentage of the total output power of the free piston engine is taken into account. In some embodiments, the amount of kinetic energy converted to electrical energy by the at least one LEM may be determined to maximize at least one of engine efficiency, engine power output, and engine emissions. In some embodiments, the amount of kinetic energy converted to electrical energy by the at least one LEM may depend on the difference between the first amount of energy stored in step 1606 and the amount of energy required for a subsequent stroke. For example, if the amount of energy stored in step 1606 exceeds the amount of energy required for subsequent strokes, the amount of kinetic energy converted to electrical energy by the at least one LEM may be equal to the excess stored, or otherwise determined for this excess storage capacity.

Step 1610 includes causing subsequent strokes after the expansion stroke to be performed without a net electrical energy input. In some embodiments, the energy stored in the drive section during the expansion stroke may provide at least some of the energy required for the subsequent stroke. In some embodiments, the energy stored in the drive section during the expansion stroke may provide all the energy required for the subsequent stroke such that no electrical energy input is required for the subsequent stroke. In some embodiments, some electrical energy may be input during the subsequent stroke, but not as much as the net electrical energy input in the subsequent stroke. For example, as described above with respect to FIG. 14, energy may be input to increase the velocity of the piston assembly or otherwise ensure that the piston assembly reaches a desired position. In some embodiments, the subsequent stroke may be a compression stroke. In some embodiments, the subsequent stroke may be an exhaust stroke.

As shown in Figure 16, steps 1602 to 1610 may be repeated for each piston cycle. In some embodiments, any or all of steps 1602 to 1610 may be repeated for each piston cycle over a number of consecutive piston cycles such that the engine continues through the consecutive number of piston cycles without net electrical energy input. to operate. For example, after receiving electrical input from the LEM for starting the engine, steps 1602 through 1610 may be repeated for each piston cycle over a number of successive piston cycles to store sufficient energy in the drive section during each expansion stroke so that Any further input from the LEM is avoided during this successive number of piston cycles. In some embodiments, steps 1602 to 1610 may be repeated such that operating conditions are continuously checked and different amounts of energy to be stored and/or converted are continuously updated to ensure that no external power input is required.

It should be understood that while the processing device is capable of determining a value corresponding to the amount of energy to be stored in the drive section, in some cases the actual stored amount may vary due to unforeseen engine wear, tolerances, environmental factors, or any other suitable conditions. May not be accurately determined. However, it is contemplated that the actual stored amount will be sufficiently close to the calculated value that there will be only minimal, if any, impact on the operation of the engine. As noted above, in some embodiments the processing device may account for these unknown losses or other suitable conditions by including a buffer in different amounts of energy to be stored.

For ease of reference, the figures may show various components labeled with the same reference numerals. It should be understood that this does not necessarily mean that identically labeled components are identical to each other. For example, the pistons designated 125 may have different sizes, geometries, materials, any other suitable features, or any combination thereof.

The foregoing is merely illustrative of the principles of this disclosure and various modifications may be made by those skilled in the art without departing from the scope of the disclosure. The above-described embodiments are provided for illustrative purposes and not for limitation. The disclosure may take many forms other than those expressly described herein. Therefore, it should be emphasized that the present disclosure is not limited to the expressly disclosed methods, systems and apparatus, but is intended to cover variations and modifications thereof within the spirit of the following claims.

Claims (30)

1. a kind of free-piston combustion engine system, including：

Cylinder, the cylinder include burning zone；

At least one free piston assembly contacted with the burning zone；

At least one drive section contacted with least one free piston assembly, wherein, at least one drive section structure Cause during the expansion stroke of piston circulation from least one free piston assembly storage energy；

At least one linear electromagnetic machine, at least one linear electromagnetic machine are used at least one free piston assembly Directly changed between kinetic energy and electric energy；With

Process circuit, in order to avoid net electric energy input, the process circuit cause during the succeeding stroke that is circulated in the piston At least one drive section is during the expansion stroke from least one free piston assembly storage at least sufficient amount Energy, to perform the succeeding stroke of piston circulation.

2. free-piston combustion engine system according to claim 1, wherein, the expansion stroke be expansion stroke and One of induction stroke.

3. free-piston combustion engine system according to claim 1, wherein, the succeeding stroke be compression stroke and One of exhaust stroke.

4. free-piston combustion engine system according to claim 1, wherein, the linear electromagnetic machine is configured in institute At least some in the energy that will be stored in the drive section are converted into electric energy during stating the succeeding stroke of piston circulation.

5. free-piston combustion engine system according to claim 1, wherein, in the described follow-up of piston circulation During stroke, the linear electromagnetic machine is configured to the energy being substantially stored in during the expansion stroke in the drive section Amount and the difference of energy of the sufficient amount be converted into electric energy.

6. free-piston combustion engine system according to claim 1, wherein, the linear electromagnetic machine is configured in institute The kinetic energy with roughly the same amount during continuing stroke in the rear is converted into electric energy during stating expansion stroke.

7. free-piston combustion engine system according to claim 1, wherein, the process circuit be configured to control by Conversion between the kinetic energy and electric energy of at least one free piston assembly that the linear electromagnetic machine is carried out, to realize most At least one of bigization engine efficiency and maximization engine power output.

8. free-piston combustion engine system according to claim 1, wherein, the process circuit is configured to described Controlled during expansion stroke the kinetic energy of at least one free piston assembly and electric energy that are carried out by the linear electromagnetic machine it Between conversion so that continue the energy conversion of desired amount in the rear during stroke by the linear electromagnetic machine into electric energy.

9. free-piston combustion engine system according to claim 1, wherein, the process circuit is configured to described At least one free piston assembly carried out by the linear electromagnetic machine is controlled during expansion stroke and the succeeding stroke Kinetic energy and electric energy between conversion so that during the expansion stroke with the rear continue stroke during be converted into electric energy The amount of energy is roughly the same.

10. free-piston combustion engine system according to claim 1, wherein, at least one drive section includes：

Gas spring；With

Passive at least one of air inlet and controllable air inlet.

11. free-piston combustion engine system according to claim 1, wherein, at least one drive section includes Gas spring with controllable geometry.

12. free-piston combustion engine system according to claim 1, wherein, the process circuit is configured to control At least one drive section, to maximize at least one of engine efficiency and engine power.

13. free-piston combustion engine system according to claim 1, wherein, the process circuit is configured to be based on At least one at least one following control free piston assembly, at least one drive section and the linear electromagnetic machine Person：The position of the piston component, the speed of the piston component, the acceleration of the piston component, the piston component Temperature, the pressure of the burning zone, the temperature of the burning zone, the potential energy of the burning zone, the chemical energy in the burning zone, The indicated work of the burning zone, the indicated efficiency of the burning zone, the fuel flow rate of the burning zone, the air of the burning zone The temperature of gas in flow rate, the pressure in the drive section, the potential energy of the drive section, the drive section, the drive section Indicated work, the indicated efficiency of the drive section, supplement air rate, the temperature of the linear electromagnetic machine, the electricity of the drive section Output, electrical efficiency, engine efficiency, engine power, previous loops performance, environment temperature, environmental pressure, emission performance and it Any combinations.

14. free-piston combustion engine system according to claim 1, wherein, the process circuit is configured to pass through At least one of control power, pressure and the volume associated with the drive section cause the drive section in the expansion stroke Period stores energy from least one free piston assembly.

15. a kind of free-piston combustion engine system, including：

Cylinder, the cylinder include burning zone；

At least one free piston assembly contacted with the burning zone；

At least one drive section contacted with least one free piston assembly, wherein, at least one drive section structure Cause during the expansion stroke of piston circulation from least one free piston assembly storage energy；

At least one linear electromagnetic machine, it is direct for being carried out between the kinetic energy and electric energy of at least one free piston assembly Conversion；With

Process circuit, the process circuit need to cause at least one drive section during the expansion stroke from it is described to The energy of few free piston assembly storage at least sufficient amount, not have net electric energy in the succeeding stroke that is circulated in the piston The succeeding stroke of the piston circulation is performed in the case of input.

16. free-piston combustion engine system according to claim 15, wherein, the expansion stroke is expansion stroke One of with induction stroke, and wherein, the succeeding stroke is one of compression stroke and exhaust stroke.

17. free-piston combustion engine system according to claim 15, wherein, the linear electromagnetic machine is configured to At least some in the energy that will be stored in during the succeeding stroke of piston circulation in the drive section are converted into electricity Energy.

18. free-piston combustion engine system according to claim 15, wherein, piston circulation it is described after During continuous stroke, the linear electromagnetic machine is configured to the energy being substantially stored in during the expansion stroke in the drive section Amount and the difference of energy of the sufficient amount be converted into electric energy.

19. free-piston combustion engine system according to claim 15, wherein, the linear electromagnetic machine is configured to The kinetic energy with roughly the same amount during continuing stroke in the rear is converted into electric energy during the expansion stroke.

20. free-piston combustion engine system according to claim 15, wherein, the process circuit is configured to control Conversion between the kinetic energy and electric energy of at least one free piston assembly carried out by the linear electromagnetic machine, to realize Maximize engine efficiency and maximize at least one of engine power output.

21. free-piston combustion engine system according to claim 15, wherein, the process circuit is configured in institute The kinetic energy and electric energy of at least one free piston assembly carried out by the linear electromagnetic machine are controlled during stating expansion stroke Between conversion so that continue the energy conversion of desired amount in the rear during stroke by the linear electromagnetic machine into electric energy.

22. free-piston combustion engine system according to claim 15, wherein, at least one drive section bag Include：

Gas spring；With

Passive at least one of air inlet and controllable air inlet.

23. free-piston combustion engine system according to claim 15, wherein, at least one drive section includes Gas spring with controllable geometry.

24. free-piston combustion engine system according to claim 15, wherein, the process circuit is configured to be based on At least one at least one following control free piston assembly, at least one drive section and the linear electromagnetic machine Person：The position of the piston component, the speed of the piston component, the acceleration of the piston component, the piston component Temperature, the pressure of the burning zone, the temperature of the burning zone, the potential energy of the burning zone, the chemical energy in the burning zone, The indicated work of the burning zone, the indicated efficiency of the burning zone, the fuel flow rate of the burning zone, the air of the burning zone The temperature of gas in flow rate, the pressure in the drive section, the potential energy of the drive section, the drive section, the drive section Indicated work, the indicated efficiency of the drive section, supplement air rate, the temperature of the linear electromagnetic machine, the electricity of the drive section Output, electrical efficiency, engine efficiency, engine power, previous loops performance, environment temperature, environmental pressure, emission performance and it Any combinations.

25. a kind of method for controlling free-piston combustion engine, the free-piston combustion engine include with accordingly at least At least one free piston assembly and at least one linear electromagnetic machine that one drive section contacts, at least one linear electromagnetic Machine is used to directly be changed between the kinetic energy and electric energy of at least one free piston assembly, and methods described includes：

Receive at least one operating characteristic of the free-piston combustion engine；

Using at least one operating characteristic described in processing circuit processes, to cause the expansion stroke that the drive section circulates in piston Period stores the energy of at least sufficient amount from least one free piston assembly, to perform the follow-up punching of the piston circulation Journey；With

Cause to perform the piston circulation in the case where unnet electric energy is input to the engine using the process circuit The succeeding stroke.

26. according to the method for claim 25, wherein, at least one operating characteristic is selected from the group of following composition：Institute State the position of piston component, the speed of the piston component, the acceleration of the piston component, the piston component temperature, It is the pressure of the burning zone, the temperature of the burning zone, the potential energy of the burning zone, the chemical energy in the burning zone, described The indicated work of burning zone, the indicated efficiency of the burning zone, the fuel flow rate of the burning zone, the air stream of the burning zone The temperature of gas, the finger of the drive section in rate, the pressure in the drive section, the potential energy of the drive section, the drive section Show that work(, the indicated efficiency of the drive section, the supplement air rate of the drive section, the temperature of the linear electromagnetic machine, electricity are defeated Go out, electrical efficiency, engine efficiency, engine power, previous loops performance, environment temperature, environmental pressure and emission performance.

27. the method according to claim 11, in addition to：Cause the linear electromagnetic machine in institute using the process circuit At least some in the energy of the free piston assembly are converted into electric energy during stating succeeding stroke.

28. a kind of system for controlling free-piston combustion engine, the free-piston combustion engine include with it is corresponding At least one free piston assembly and at least one linear electromagnetic machine of at least one drive section contact, it is described at least one linear Electromagnetic motor is used to the kinetic energy of at least one free piston assembly being directly changed into electric energy, and the system includes：

At least one sensor, at least one sensor is connected to the free-piston combustion engine, for measuring State corresponding at least one operating characteristic of engine and for exporting corresponding at least one sensor signal；

At least one controlling organization, for adjusting the free-piston combustion engine based on corresponding at least one control signal Corresponding at least one operating characteristic；With

Process circuit, the process circuit as input and export at least one sensor signal described at least one Control signal, the process circuit are configured to：

At least one sensor signal is handled, to cause at least one drive section described using the controlling organization From the energy of at least one free piston assembly storage at least sufficient amount during expansion stroke, with what is circulated in the piston There is no net electric energy performs the piston circulation succeeding stroke in the case of inputting in succeeding stroke.

29. system according to claim 28, wherein, at least one sensor is selected from the group of following composition：Position Sensor, velocity sensor, accelerometer, temperature sensor, pressure sensor, flow rate sensor, current sensor, voltage pass Sensor, electric resistance sensor, impedance transducer, vibrating sensor, motion sensor, force snesor and emission sensor.

30. system according to claim 28, wherein, the process circuit is also configured to cause using the controlling organization At least some in the energy of the free piston assembly are converted into electricity by the linear electromagnetic machine during continuing stroke in the rear Energy.